During the life span of an ink jet pen, air or gas bubbles develop in the ink and coalesce into larger bubbles. As the bubbles form and coalesce, they tend to accumulate in the ink feed port, filter areas and ink feed channels of the ink pen. If the amount of air or gas bubbles increases significantly, performance of the pen may be affected. For disposable pens, air accumulation is not typically a significant problem. However, for longer life permanent or semi-permanent pens having a cartridge body and a separate replaceable ink cartridge, and for high quality, high speed printing devices, substantial air or gas bubble accumulation may be a problem.
Some of the air or gas bubbles in the ink flow channels of the pen are removed from the pen through ink ejection orifices of the pen during priming. However, a portion of the air or gas bubbles may find its way back through the ink feed paths into the ink feed port in the connection between the cartridge body and the ink cartridge. Air or gas bubbles may also accumulate in the ink feed port between the cartridge body and ink cartridge by other mechanisms. As ink is introduced into the ink cartridge, an amount of dissolved air is included with the ink. As the ink is heated in the cartridge or printhead, its capacity for dissolved air decreases and the air or gas bubbles are released from the ink. Another source of air or gas bubbles in the ink feed port of a pen arises from the removal and connection of ink cartridges with the cartridge body. If a spent ink cartridge is allowed to run dry of ink, air will fill the ink feed port connecting the cartridge to the cartridge body. Even if the ink cartridge is not run dry of ink, a certain amount of air is introduced into the ink feed port each time an ink cartridge is connected and/or disconnected from the cartridge body.
Priming the pen by ejection of ink may remove air or gas bubbles from the printhead itself, however, there may still be a substantial amount of air in the ink feed port due to ink cartridge replacement. This air is effectively trapped between the cartridge body and the ink cartridge in the connection port connecting the cartridge to the cartridge body.
An object of the invention is to provide an apparatus and method for removing air and gas bubbles from an ink jet pen.
Another object of the invention is to provide a device for removing a substantial quantity of air and a minimum amount of ink from an ink feed port.
Still another object of the invention is to provide a substantially automatic air removal system which is activated upon ink cartridge replacement.
Another object of the invention is to improve the operation of a permanent or semi-permanent ink jet pen.